Drill bits adapted to bore through rock for the installation of roof mounts in mines and the like have a hardened carbide blade mounted in a transverse slot at the distal end of an elongate hollow tubular body. The body also has access ports communicating with the inner bore, located adjacent the distal end of the body. The blades of such drill bits are adapted to drill a hole having a diameter of approximately one inch and larger into the stone roof of a mine. A vacuum may be drawn through the hollow drill bit such that stone cuttings removed by the blade are drawn through the ports, through the hollow shaft of the drill bit, and to a collection location remote from the drilling.
Alternately, a water flushing system may be used in which pressurized water is force through the drill steel and out the ports to wash the cuttings out the mouth of the hole.
Presently, it is the practice to attach a drill blade in the slot at the distal end of a drill body by brazing. Prior to being brazed, however, the blade may easily slide from side to side within the slot, and as a result the blade is frequently brazed into a position which is not centered within the slot with respect to the axis of rotation of the drill bit during use thereof.
The blades of such drill bits are subjected to extreme forces causing stresses within the blade which frequently result in breakage of the blade and failure of the bit. The failure of the blade is frequently attributable to improper alignment of the blade on the distal end of the drill bit body, but may also occur as a result of the excessive thrust applied to the blade during the drilling operation. Frequently, failure of a drill bit occurs when the blade first fractures along its longitudinal centerline.
It would be desirable to provide an improved drill bit blade and drill bit body which would reduce the incidences of misalignment of the blade at the distal end of the body, and further would provide greater thrust bearing capacity in the center portion of the blade, thereby reducing the incidences of failure of the drill bit, and extending the life thereof.